$-bc + 8bd - 2b - 3 = 9c - 10$ Solve for $b$.
Combine constant terms on the right. $-bc + 8bd - 2b - {3} = 9c - {10}$ $-bc + 8bd - 2b = 9c - {7}$ Notice that all the terms on the left-hand side of the equation have $b$ in them. $-1{b}c + 8{b}d - 2{b} = 9c - 7$ Factor out the $b$ ${b} \cdot \left( -c + 8d - 2 \right) = 9c - 7$ Isolate the $b$ $b \cdot \left( -{c + 8d - 2} \right) = 9c - 7$ $b = \dfrac{ 9c - 7 }{ -{c + 8d - 2} }$ We can simplify this by multiplying the top and bottom by $-1$. $b= \dfrac{-9c + 7}{c - 8d + 2}$